Typically, corrugated cardboard panels are comprised of two flat outer sheets and an internal corrugated liner sheet which spaces the two outer sheets apart and defines the overall thickness of the cardboard. Together, these outer sheets and the corrugations or undulations in the internal sheet define a series of "flutes" which are parallel linear passages or tunnels adding strength and rigidity to the panel structure.
The outer sheets and the internal sheet are glued together in a machine commonly known as a corrugator that is well known in the art and comprises a series of stations which respectively perform a variety of functions, e.g., lay up of the outer sheets with the internal sheet, application of a starch based glue to the sheets which are then arranged in a sandwich form, etc. After the sandwich is formed, the corrugated cardboard is passed over a hot plate in what is known as a double backer section of the corrugator. The bottom outer sheet rides on the hot plate and the sandwich is pulled along by means of an overhead endless belt engaging the top outer sheet. The hot plate extends the full width of the panel and along a predetermined length thereof to properly dry and cure the glue.
To ensure an even distribution of glue, the panel runs under a plurality of parallel steel rollers which are longitudinally spaced from each other to apply a hold-down force against the panel by exerting their weight through the belt against the top outer sheet. In prior art double backer systems of which I am aware, the rollers extend between a pair of parallel side frames and are respectively mounted, via bearings at opposite ends thereof, to a pair of pivotal support arm assemblies connected to the side frames. The support arms are controlled to mechanically or manually move the rollers between upper and lower positions. In the lower position, the rollers ride on the top outer sheet in the manner described above. However, if one or more of these rollers is off center, e.g., which may be caused by a gradual buildup of glue at one or both bearings, then the roller surface will no longer be parallel to the panel surface and will likely exert a crushing force against the panel. This crushing force will either adversely affect the strength of the panel or result in a crease in the panel, either occurrence requiring the panel to be discarded as scrap.
It is accordingly one object of the present invention to provide a roller system in a double backer which does not exert a crushing force against the cardboard panel being manufactured.
Another object is to provide a roller system which is self-adjusting to maintain parallelism between the roller surfaces and the cardboard panel.
Yet another object is to provide a roller system which automatically adjusts its position to exert a substantially uniform downward clamping force against the cardboard panel along the entire width of the panel.
Yet another object is to provide a no-crush roller system in which self-adjustment occurs as a result of eccentric bearing mounts rotatably supporting opposite ends of each roller.